Anyone who has walked through Zuccotti Park in recent days will be left in little doubt about the intention of Occupy Wall Street protesters to push on through the winter. Huge military-style canvas tents designed to withstand plunging temperatures have sprung up among dozens of smaller, two and three-person pods. One, marked with a red cross, offers flu shots, while another offers a safe space for women.

But as the diehards in New York and other encampments across the US prepare to dig in, organisers are facing their next big challenge: what next?

In a tacit admission that the protests will be difficult to sustain over the winter, organisers are now focusing their efforts on planning a "spring offensive" with fresh targets, they told the Guardian in a series of interviews this week.

Details of the campaign will be unveiled later this month, according to the activists who say they will spend the winter consolidating their position, broadening their support base and refining communication between Occupy grounds nationwide, using online tools being developed by their IT team.

Keeping the protests alive at all through the cold months is becoming a challenge for a movement flushed with the dramatic success of its first eight weeks.

The Guardian has learned that Adbusters, the Canadian activist group which helped spark the movement, is even considering calling on occupiers to declare "victory" for phase one and go home for the winter – clear recognition that numbers are likely to dwindle anyway and make it increasingly difficult for the protests to maintain momentum and generate headlines.

In its first few weeks, the grassroots protest spread from New York to hundreds of towns and cities globally. It altered political discourse, forced debate away from the deficit towards inequality and, via a series of high-profile actions, marches and – most dramatically – clashes with police, shot up the news agenda worldwide.

But now there are signs that public interest is tailing off, with resources such as Factiva and Google Trends appearing to show a drop in searches for "Occupy Wall Street" over recent weeks. Media coverage, too, is dwindling.

At Zuccotti Park, activists acknowledge that there has been a lull. But they say that, as a measure of the movement's success, it is irrelevant.

Activist Justin Wedes, who beckoned me to follow him to a meeting as we talked, said: "If the mainstream media has shifted their focus off Occupy Wall Street it doesn't mean we are not growing as a movement. We are growing every day and new occupations are cropping up."

As we moved from the east side of the encampment to the west, Wedes greeted fellow activists, exchanging high-fives with some and patting others on the shoulder.

He said: "We never intended to rely on the mainstream media to put out our message. In two months we have established hundreds of media centres, 24/7 live streaming, and traditional print media in the form of Occupy Wall Street Journal. People are becoming citizen journalists. In the reporting of the movement, we are making the mainstream media irrelevant right now."

He said that they plan now to communicate better internally and that, inside a nearby media tent, people were working on online tools to facilitate general assemblies between Occupy encampments in separate locations.

Activists in the leaderless movement readily admit that ensuring consensus in a non-hierarchical has its challenges. But they are adamant that the fledgling movement is sustainable.

"The tactic of physical occupation worked very well at the beginning," said another activist, Jonathan Smucker. "It was a powerful symbol of defiance against some of the most powerful people in the world who are widely recognised as being culpable for the economic situation we are in. As a way of achieving a goal or being in a better position to achieve a goal, it has been enormously successful. Overnight and for the last month, we have changed the narrative around the economy and society. But we risk being defined by that one tactic as opposed to the values that are resonating with people. It's not an easy thing to navigate.

"We can't keep replicating the same tactic and expect the same level of success. The challenge is, what do you do? How do you find another way to strike that chord with more people?"

Smucker believes that the shift in debate is a backdrop which enables political change. He cites the example of Ohio, where this week a Republican-backed law curbing collective bargaining rights was voted out by a margin of almost two to one, after a union campaign.

"I think something does happen when you have a national shift. The Tea Party changed the backdrop of all sort of fights in the past two years. We have to take the long view."

Smucker is confident that an idea will emerge that will provide the momentum for the next step.

"We have more than 50 working groups. Somewhere, one of those conversations will have a great idea and we will forward it and it will be the next thing that will give momentum."

Kalle Lasn, the editor-in-chief of Adbusters, said it was considering declaring victory in an attempt to regain the initiative after a series of negative headlines about the encampment.

"We are talking about it with all our people," said Lasn. "The other side is owning the narrative right now. People are talking about drugs and criminals at OWS.

"Why not, as a grand gesture, declare victory? I love the idea that some diehards will dig in through the snow. This is what happens in movements and revolutions, they have this crazy wild state a the beginning where nobody knows that going on."

Even among those sympathetic to the Occupy movement, there is some skepticism as to whether it is sustainable in its current form.

Chris Howell, a professor of politics at Oberlin College, said the movement had been successful in shifting political discourse from the budget deficit to inequality of power and wealth. But he said that to move beyond that it needed to institutionalise itself.

"There is a strong anarchist – in the best sense of the word – emphasis on radical democracy in the movement and that makes if hard to create an organisation," said Howell. "To create a party platform, to create leaders, all these things are required to put down roots.

"This is a movement resistant to institutionalisation. I know why, but I don't know how they can move forward in that way. There are very few people – students perhaps – that can be permanently mobilised."

OWS activists disagree. A leaderless, non-hierarchical movement has got them this far and they plan to continue in the same vein.

At 60 Wall Street, an atrium at the foot of a 55-floor skyscraper that serves as the American headquarters of Deutsche Bank, where activists and organisers from the Occupy Wall Street working groups have taken to holding their meetings, the direct action group were deep in discussion.

Michael Premo, 29, an activist on the direct action and the outreach team, said the movement needed to reach out to different and more divergent groups. He compared the Occupy movement to the civil rights movement. "That was everything from electoral reform to complete separatism. You had W. E. B. Du Bois advocating integration and Booker T Washington arguing for separatism," Premo said. "Du Bois and Washington were civil rights leaders on opposite sides of the black civil rights movement.

"If it's going to include and never exclude people who feel disenfranchised by the current government system OWS can never have demands," Premo said. "A certain segment of it can have demands. Even though I believe the movement is beyond electoral politics, some people may believe electoral politics is important."

He said the winter would be a reflective time "to dream" and then the movement would launch its "spring offensive".

It would include civil disobedience, he said, adding: "The only way we will get the level of media interest we have had is through civil disobedience."

While Democratic politicians have responded favourably to the movement, with Barack Obama saying they reflect "the frustration" that many struggling Americans are feeling, OWS protesters remain unwilling to align themselves with any political party.

But, as with any movement, there is a spectrum of political hues and there has emerged at least one group keen to take a more active role in the upcoming elections. This week, a spokesperson for Occupy Cincinnati told the Associated Press they were vetting six potential candidates for local office from Ohio, New York and Kentucky.

Wedes stressed that it had not been endorsed by the general assembly – at least not yet. "That's not a consensus decision," said Wedes. "There's no plan for an independent or third party OWS at this point."

But first there is the winter to get through. "We've captured the imagination of the world," said Lasn of Adbusters. "Now we need to have a winter brainstorming and we'll come up with a myriad projects."